The life of creature, e.g., birth, senescence, disease, and death, is the most interesting and important subject of life sciences. Of the life processes, senescence is a natural part of the development, and eventually causes death of creatures. Thus, with the eventual aim of the retardation of senescence in living organisms, active and extensive research has been and is being conducted on causes and control mechanisms of senescence all over the world. Studies on the control mechanisms of senescence-related genes in plants as well as animals are underway.
Plant senescence is defined as the sequence of biochemical and physiological events in the final stage of plant development. The changes taking place simultaneously or separately in various tissues of a whole plant or in plant tissues such as leaves, flowers or fruits. Plants senescence may be induced by a variety of external factors or stimulators (such as light flux, shading, temperature, water, stress, pathogen attack etc.) as well as internal factors (such as plant growth regulators: ethylene, abscissic acid, cytokinins, auxins etc. and carbohydrate metabolism). When the above condition taking place, a genetic switch is triggered to modify gene expression at the transcriptional and/or post-transcriptional level and induces a change in cell and tissue functions resulting in senescence. If the genes and their regulation regions involved in the induction or retardation of plant senescence are studied and applied in plant science industry, the productivity and economic values can be increased significantly without the environmental destruction caused by the usage of regulatory chemicals.
Furthermore, the promoter used mostly for the gene expression in plant transformation is tobacco mosaic virus 35S promoter that is expressed generally in various tissues and developmental stages of a plant. Hence, tobacco mosaic virus 35S promoter is not suitable for the tissue specific or senescence specific gene expression. It is also not suitable while the general gene expression may cause damage to the plant. Applying a promoter with tissue specificity and developmental stage specificity may be a good solution for the above conditions.